Studies on virulence and host resistance in Oat Blumeria graminis f sp avenae pathosystem

Abstract

newline The investigation entitled Studies on virulence and host resistance in Oat- Blumeria graminis f. sp. avenae pathosystem was conducted at Department of Plant Pathology, CSKHPKV Palampur during 2016-2020. Powdery mildew of oat caused by Blumeria graminis D.C. (Speer) f. sp. avenae Em. Marchal is the most deleterious foliar disease of cultivated oat and severe losses of green fodder and grain yield has been reported in North Western Himalayas. Total 24 isolates of B. graminis f. sp. avenae causing powdery mildew were collected from 6 districts belonging to different zones of Himachal Pradesh. On the basis of symptomatology, the disease was identified as powdery mildew of oat and on the basis of morphological and molecular characterization, the pathogen causing powdery mildew of oat was identified as Blumaria graminis f. sp. avenae. To identify the resistant sources, 303 oat germplasm lines were evaluated under field conditions for 3 years and 11 lines viz., JPO-40, OS-10, OG-77, PLP-1, OL-1847, OL-1869, OL-1689, OL-1689-AVTSC, HFO-864, HFO-125 and OL-6 were found resistant. Among 19 accessions belonging to 12 species of Avena also evaluated under field conditions and none of the accessions of any species was found highly resistant, however, OG-77 (A. sativa) and HFO-864-16 (A. byzantina) were found resistant against powdery mildew pathogen. The cultivars IG-03-203, JPO-20 and KRR-AK-06 were identified as slow mildewers on the basis of low values of AUDPC, high incubation and latent period, smaller size of colonies, less sporulation as represented by number of conidiophores bearing conidia per colony as compared to highly susceptible check HJ-8. Differential set of 11 lines viz., ADG-96, HFO-102, IG-03-213, JPO-40, OL-1847, OG-77, PLP-1, JO-11, OL-1867, UPO-212 and susceptible check HJ-8 was developed to study the pathogenic variability of B. graminis f. sp. avenae causing oat powdery mildew. Study of pathogenic variability on developed differential set grouped 24 isolates into 14 pathotypes (OMP-1 to OMP-14) and the isolates were grouped in different pathotypes as per their geographical locations. The OMP-2, OMP-7 and OMP-13 were highly virulent among all the pathotypes, which gave susceptible reaction on 9 out of 11 differential lines. Analysis of genetic diversity of 22 isolates of B. graminis f. sp. avenae using 4 polymorphic ISSR markers formed 12 groups at 98 per cent similarity coefficient indicating high genetic diversity among isolates. Both the pathogenic and molecular variability showed wide diversity among population of B. graminis f. sp. avenae in Himachal Pradesh. The inheritance of resistance was studied by makig crosses of 3 resistant lines i.e. OL-1847, OG-77 and OL-1689 with highly susceptible cv. HJ-8. In all three crosses, F1 population was found resistant to powdery mildew and F2 generation segregated into three resistant and one susceptible plant ratio, which confirmed that the resistance to oat powdery mildew was controlled by single dominant gene. newline newline